Imec looks to extend capabilities of Gallium Nitride (GaN) technology

August 12, 2015 // By Graham Prophet
Nano-electronics research centre imec (Leuven, Belgium) is extending its Gallium Nitride-on-Silicon (GaN-on-Si) R&D programme, and is now offering joint research on GaN-on-Si 200mm epitaxy and enhancement mode device technology.

The extended R&D initiative includes exploration of novel substrates to improve the quality of the epitaxial layers, new isolation modules to increase the level of integration, and the development of advanced vertical devices. Imec’s is offering participation in its programme to new partners interested in next-generation GaN technologies and to companies looking for low-volume manufacturing of GaN-on-Si devices to enable the next generation of more efficient and compact power converters.

GaN technology [already] offers faster switching power devices with higher breakdown voltage and lower on-resistance than silicon, making it an highly-performing material for advanced power electronic components.

Imec’s R&D programme on GaN-on-Si was launched to develop a GaN-on-Si process and bring GaN technology towards industrialisation. Building on imec’s track record in GaN epi-layer growth, new device concepts and CMOS device integration, imec has now developed a complete 200-mm CMOS-compatible GaN process line. Imec’s GaN-on-Si technology is reaching maturity, and companies can gain access to the platform by joining imec’s GaN-on-Si industrial affiliation program (IIAP). The process line is also open to fabless companies interested in low-volume production of GaN-on-Si devices tailored to their specific needs, through dedicated development projects.

Imec’s portfolio includes three types of buffers optimised for breakdown voltage and low traps-related phenomena (i.e. current dispersion): a step graded AlGaN buffer, a super lattice buffer, and a buffer with low-temperature AlN interlayers.

[Note: GaN devices for power applications are typically diffused in a layer of GaN grown on a dissimilar substrate – most often silicon, although sapphire and even diamond are also used. The dissimilar crystal lattices of the GaN and the substrate mean that the GaN epitaxial layer cannot be grown directly on the substrate: a buffer structure must be employed to manage the transition between the crystal lattices, to avoid formation of dislocations and poor mechanical performance of the combined material.]

Imec has explored side-by-side enhancement mode power devices of the MISHEMT and p-GaN HEMT type, as well as a gate-edge terminated Schottky power diode featuring low reverse leakage and low turn-on voltage. The latest generation of imec enhancement mode power devices shows a threshold voltage beyond +2V, an on-resistance below 10 ohm mm and output current beyond 450 mA/mm. These devices represent, imec believes, the state of the art of enhancement mode power devices.